I haven't been in a few years, but Paul Martin's at the Spectrum had the best cheeseburger hands down I've had anywhere. It used to be around $12, but I think so many people would order it compared to their otherwise less than memorable more expensive entrees, they raised the price every year to the point it's now $20+, and there's often a wait. So, not worth the hassle most of the time (hence why I haven't been back). But if you don't mind the wait, they make their own patties, everything is fresh, and overall it's the platonic ideal of a cheeseburger.
As for less expensive and more convenient options, Hopdoddy and Mooya are both pretty good. I don't love The Cut. The Stand was fine but not memorable to me. Wendy's really isn't bad at all for fast food, I like that they don't freeze their patties, you can taste the difference.